In a component as mentioned above, the drift zone serves to take up, in the off state, a space charge zone that propagates proceeding from a component junction between the drift zone and a further component zone. In the case of a MOSFET or IGBT, said component junction is a pn junction and the further component zone is the body zone of the MOSFET or IGBT, said body zone being doped complementarily with respect to the drift zone. In the case of a diode, the component junction is likewise a pn junction and the further component zone is that zone from among the anode and cathode zones which is doped complementarily with respect to the drift zone. In the case of a Schottky diode, the component junction is a Schottky junction and the further component zone is a Schottky contact.
An SOI component realized as a MOSFET is described in DE 101 06 359 C1 or WO 2005/076366 A2, the source terminal and drain terminal of said component being connected to the semiconductor substrate via semiconductor zones doped complementarily with respect to the semiconductor substrate. In this case, the terminal of the terminal contacts to the semiconductor substrate has the effect that, when the component is driven in the off state, a space charge zone propagates in the semiconductor substrate as well as in the drift zone along the insulation layer. Said space charge zone leads to a reduction of the voltage loading on the insulation layer. In order to influence the field distribution in the semiconductor substrate, even further semiconductor zones doped complementarily with respect to the semiconductor substrate, so-called field zones, may be provided in the substrate beneath the insulation layer.
When realizing semiconductor components having a drift zone, it is desirable, in principle, to achieve a highest possible dielectric strength when the component is driven in the off state and a lowest possible on resistance when the component is driven in the on state. However, the optimization of one of these component parameters is usually detrimental to the other of the two parameters unless additional measures are implemented. Thus, a reduction of the on resistance can be achieved for example by means of an increased doping of the drift zone. However, the dielectric strength decreases in this case.
Additional measures which lead to a high dielectric strength despite a high doping of the drift zone consist, in the case of so-called compensation components, in providing in the drift zone compensation zones that are doped complementarily with respect to a drift zone. Compensation components of this type are described for example in U.S. Pat. No. 5,438,215 or DE 43 09 764 C2.
In the case of field plate components described for example in U.S. Pat. Nos. 4,903,189 or 4,941,026, provision is made of a field plate that is arranged adjacent to the drift zone and is insulated dielectrically from the drift zone. Said field plate comprises a metal or a highly doped polysilicon and is at a predetermined potential, for example the potential of one of the load terminals of the component. Said field plate serves, in the off-state case, to compensate for a portion of the dopant charge present in the drift zone. This compensation effect enables a higher doping of the drift zone, and hence a lower on resistance, for the same dielectric strength of the component.
U.S. Pat. No. 5,844,272 describes a lateral MOSFET in which the gate electrode is arranged adjacent to a body zone and has a more weakly doped gate extension that runs along the drift zone and is insulated from the drift zone by means of a dielectric layer. When the component is driven in the on state, the gate extension brings about the formation of an accumulation channel in the drift zone along the dielectric layer and thus brings about a reduction of the on resistance. In the off-state case, a space charge zone that depletes the gate extension of charge carriers likewise forms in the gate extension due to a space charge zone that propagates in the drift zone.
Accordingly, it would be desirable to provide an SOI component having a high dielectric strength and a low on resistance.